The present invention relates to the diagnostic imaging arts. It particularly relates to nuclear medical imaging using gamma cameras each including at least a two-dimensional scintillation detector and a collimator, and will be described with particular reference thereto. However, the invention will also find application in conjunction with other imaging modalities.
In nuclear medical imaging, a subject is administered a radiopharmaceutical by ingestion, injection, or another delivery pathway. The radiopharmaceutical is preferably absorbed by one or more organs of interest, such as bone tissue, the liver, the heart, the vascular system, tumors, or other organs or tissues. Radiation generated by the radiopharmaceutical is emitted from the body and detected by one or more detector heads of a gamma camera. Each detector head typically include a scintillation crystal or crystal array facing the subject and an array of photomultiplier tubes, photodiodes, or other optical detectors arranged to detect scintillation events due to radiation impinging upon the scintillation crystal.
A collimator of lead or another radiation-absorbing material is mounted to each head between the scintillation surface and the subject. Typically, the collimator includes a honeycomb of bores that define the trajectory of received radiation. The collimators of lead or other material are usually fairly massive, often weighing around 100 pounds to 300 pounds each, and are detachable so that an optimally designed collimator can be installed for a particular imaging session. Optionally, energy-selective filters are also interposed in front of the detector face. The filter can be integrated into the collimator.
Typically, a nuclear camera includes a family of collimators. Thicker collimators with small bores provide higher resolution. Thinner collimators and collimators with larger bores provide higher count rates. Collimators whose bores are angled are used for magnification and reduction imaging. Specialized collimators that focus on two displaced regions of the subject are also used.
Typically, the patient is brought into the imaging suite and positioned on a patient couch of the nuclear camera. The operator selects a diagnostically appropriate protocol for the patient's medical condition on an imaging console. In more sophisticated nuclear cameras, the console can determine whether the appropriate collimator for the scan is on the nuclear camera heads. In other nuclear cameras, the operator manually inspects the collimators to determine if the right collimator is present.
In most instances, the collimators need to be changed. To change the collimators, the operator moves the detector heads to the appropriate collimator changing position. The operator then rolls in a collimator holding cart, which supports the currently installed collimators as they are disconnected. The cart is then used to transport the collimators to a storage location where it is further used to pick-up the proper set of collimators. The appropriate set of collimators on the cart are wheeled up to the detector heads and manually mechanically coupled. This operation typically requires 10-15 minutes of operator time.
If the nuclear camera is equipped with an automatic collimator exchanger as shown in U.S. Pat. No. 5,519,223 issued to Hug, et al, the operator leaves the imaging console and crosses the room to the collimator exchanger. On a control panel for the collimator exchanger, the operator selects the appropriate collimators and instructs the exchanger to start.
Once the collimators have been changed, the detector heads are moved from the collimator changing position to the appropriate orientation for imaging. In most nuclear cameras, the operator uses controls located on the gantry to move the detector heads manually to the proper position. On some nuclear cameras, the operator codes the desired detector head position on the gantry control and the gantry then rotates the detector head to the selected angular position. Once the detector head is in the selected angular position, the proximity of the detector head to the patient is controlled by the operator at the gantry.
Once the heads are appropriately positioned angularly, and distance-wise, the operator then moves the heads to the appropriate position along the patient for the imaging procedure.
Once the appropriate collimators have been mounted and the heads properly positioned, the operator returns to the imaging console and conducts an imaging procedure with the selected protocol. During the whole set-up procedure, the operator either left the patient unattended, or a second attendant was employed to comfort the patient.
The set-up for a selected imaging procedure typically includes: installing a suitable collimator and optional energy-selective filter; positioning the patient relative to the detector heads by moving at least one of the patient support, the gantry, or robotic arms that carry the heads; setting up initial positions for the detector heads with each head position including at least a rotational setting, a detector cant or tilt, and a detector head proximity to the patient. These set-up procedures can take up to 15 minutes or more, and involve substantial intervention of the operator.
Daily quality control procedures which verify and maintain camera alignment and the like are similarly time-consuming and labor-intensive.
The present invention contemplates an improved apparatus and method that overcomes the aforementioned limitations and others.